Synthesis and structural characterization of some selenoruthenates and telluroruthenates

摘要

The reaction of solid [RuCICp(PPh3)(2)] with TeSe32- or Se-n(2-) in DMF leads to the formation of [RuCp(PPh3)(μ(2)-Se-2)](2) (1). In the structure of this compound the two bridging Se-2 groups lead to a six-membered Ru2Se4 ring in a chair conformation. Attached to each Ru center is a PPh3 ligand in an equatorial position and a Cp ring in an axial position. The compound is diamagnetic. The compound [Ru2Cp2(μ(3)-Se-2)(μ(3)-Se)](2)(2) is obtained under similar conditions in the presence of air. This structure comprises a centrosymmetric RU4Se6 dimer formed from the two bridging Se groups and the two bridging Se2 groups. Each Ru center is π-bonded to a Cp ring. The reaction of solid [RuCICp(PPh3)(2)] with a Te-n(2-) polytelluride solution in DMF leads to the diamagnetic compound [(RuCp-(PPh3))(2)(μ(2)-(1,4-η:3,6-η)Te-6)] (3). Here the Ru centers are bound to a bridging Te6 chain at the 1, 4, 3, and 6 positions, leading to a bicyclic Ru2Te6 ring. Each Ru atom is bound to a Cp ring and a PPh3 group. This dimer possesses a center of symmetry. The structure of 3 is the first example of a bicyclic complex where fusion occurs along a Te-Te bond. If the same reaction is carried out in DMF/CH2Cl2, rather than DMF, then [(RuCp(PPh3))(2)-(μ(2)-(1,4-η:3,6-η)Te-6)]-CH2CI2 (4) is obtained. In the solid state it possesses the same Ru2Te6 structural unit as does 3, but the unit lacks a crystallographically imposed center of symmetry. The electronic structures of 3 and 4 have been analyzed with the use of first principles density functional theory. Bond order analysis indicates that the Te-Te bond where fusion occurs has a shared bonding charge of about (2)/(3) of that found for Te-Te single bonds.